1. Field of the Invention
The present invention relates to a pipe handle formed by coupling a plurality of pipes and to a cleaning device having the pipe handle and a head.
2. Description of the Related Art
There have been known cleaning devices composed of a pipe handle and a head connected to one end of the pipe handle. Cleaning devices of this type are typically used with a disposable cleaning sheet (e.g., a wiper of nonwoven fabric) attached to the head. When used for cleaning the house floor or the like, the pipe handle need be so long that the head can slide on the floor surface with a grip (the other end of the pipe handle) being held by hand.
Japanese Unexamined Patent Publication Nos. 2002-005135 and 2002-081420 disclose pipe handles which are constructed by coupling a plurality of pipes to have a certain length.
Firstly, they disclose coupling between a larger diameter pipe and a smaller diameter pipe, wherein one end of the smaller diameter pipe fits in one end of the larger diameter pipe.
In this case, however, the smaller diameter pipe may be too thin to withstand a bending stress during use, particularly when the pipe handle is constructed of three or more pipes. The bending stress exerted on such a long object is proportional to the bending moment and is inversely proportional to the modulus of section, but in case where the pipe wall thickness is constant, the modulus of section decreases as the outside/inside diameter decreases. Therefore, the use of the smaller diameter pipe may increase the bending stress due to the bending moment during cleaning, which lowers the bending strength.
Secondly, they disclose that a male coupling (or male side end part) of one pipe diametrically contracts toward a distal end to have two-stage tapered outer surface, a proximal second tapered outer surface having a steeper gradient than a distal first tapered outer surface, and a female coupling (or female side end part) of the other pipe has a tapered inner surface whose gradient is equal to that of the first tapered outer surface so that the two pipes can be coupled together by fitting the tapered inner surface of the female coupling over the first tapered outer surface of the male coupling.
In this case, however, since the pipe has to be circumferentially contracted to produce the first and second tapered outer surfaces, the pipe wall thickness tends to vary in the contracted portion, which makes it difficult to hold dimensions of the first tapered outer surface to close tolerance. If the dimensions of the first tapered outer surface cannot be held to close tolerance, insertion of the male coupling into the female coupling will be difficult due to tightness or the male coupling will wobble within the female coupling due to looseness. In addition, such contracting, which is typically performed by clamping and deforming a pipe end between rolls, requires an expensive processing equipment for holding the dimensions to close tolerance and requires some experience, which also results in high cost.
Moreover, since the first tapered outer surface, which is formed by diametrically contracting the male side end part, has a relatively small diameter, the strength against bending moment decreases as set forth above. Furthermore, the first tapered outer surface formed by diametrically contracting the pipe tends to fatigue due to residual stress. Therefore, if the bending stress concentrates in the connection between the pipes during cleaning, bending or cracking tends to occur in the first tapered outer surface.
Japanese Unexamined Patent Publication No. 2002-005135 further discloses a sleeve which is to be located around the male and female couplings of the two pipes. Coupling between the two pipes can be maintained by fitting an engaging projection, which is formed on an inner surface of the sleeve, into both an engaging hole of the male coupling and an engaging hole of the female coupling.
In order to fit the engaging projection into the engaging holes, the sleeve need be slid on the pipe after coupling. However, as the sleeve is slid on the pipe, the engaging projection also comes into contact with the pipe to resist sliding. In addition, it is impossible to visually confirm whether the engaging projection has fitted in the engaging holes from the outside.